Electric power transformer



July 10, 1934,

c. w. GALTON 1,965,739

nmcmc POWER TRANSFORMER Filed Sept. 16, 1932 Ckqrh: 5 W "10,61 6a.!

INVENT R,

Patented July 10, 1934 UNITED STATES ELECTRIC rowan TRANSFORMER Charles William Galton, Lampton, England Application September 16, 1932, Serial No. 633,402 In Great Britain September 17, 1931 1 Claim.

The present invention relates to step-up electric power transformers and the principal object is to provide an efiicient transformer having an inherent high power factor and also having -Ineans which are an integral part of the transformer for varying or adjusting the secondary voltage and current to suit different consuming devices in the secondary circuit. Another object is to provide such a transformer which will provide within limits automatic adjustment of the secondary voltage to maintain constant current through a consuming device liable to variation in resistance.

The invention is directed to the supply of ourrent to gas discharge tubes or bulbs or the like which normally require voltages in excess of that usually obtained from ordinary supply lines and are liable to variation of resistance during their life.

It is known that integral means for adjustment have been adapted 'to. step-up leakage transformers but hitherto for step-up transformers with tight or close coupled primary and secondary coils it has been found necessary to use resistances, choke coils, reactor coils, or some like device which is external to the transformer itself, and which operates on only one winding of the transformer, in order to obtain variation of the secondary voltage or current.

A step-up transformer according to the present invention comprises close coupled primary and secondary windings on one limb of a closed magnetic circuit and an auxiliary winding or windings on a limb of a branch magnetic circuit which limb is separated from the other portion of the latter circuit by a fixed or adjustable air gap or gaps, the said auxiliary winding or windings being connected or adapted to be connected in series with the primary winding or in part in series with the primary and in part in series tion may be carried out. Figure 1 represents in elevation one illustration of applicants invention, and Figure z represents in elevation a modification thereof.

In the arrangement shown in Figure 1 the close coupled primary winding P and secondary windings are wound on the limb L of the closed (10 magnetic circuit M, and a branch magnetic circuit M is provided on a limb L of which the auxiliary winding A is wound in sections A A A two of which are connected together and in series with the primary, with the remaining one open and idle. The primary winding and the sections A A of the auxiliary winding, thus 00 nected in series, are connected with the source of supply E. The limb L is separated from the other portion of the branch magnetic circuit M 7 by adjustable air gaps G whereby the magnetic reluctance of this branch may be varied, to suit the secondary output requirements of different consuming devices, and also to vary as a whole the intensity of the effects produced by the auxiliary coils as now to be described. With sections of the auxiliary winding connected in circuit, as shown, the'arrangement provides within limits automatic adjustment of the secondary voltage'to maintain constant current through a consuming device liable to variation in resistance. It will be seen for instance that if the resistance of the device decreases the current in the secondary winding ,will tend to increase and that this increase reacts to produce an increase of current in the auxiliary winding and thus to increase the contra magneto-motive force and decrease the flux through the coupled primary and secondary windings, thereby reducing the tendency to increase of current in the secondary winding and through the consuming device. A balance is thus struck with an increase of current in the secondary winding which is less than would have been the case in the absence of the auxiliary winding. Thus within certain limits a degree of automatic adjustment of output to load will be obtained. The auxiliary windings will of course sistance,

In Figure 2' the arrangement of magnetic circuits and windings is similar to that shown in Figure 1 with the exception that one auxiliary winding A is joined in series with the primary winding, another coil A is open and idle and the remaining winding A is connected across a suitable non-inductive energy consuming device C which may consist of a simple fixed resistance.

The effect of the auxiliarywinding A connected in series with the primary winding P is as previously described. With regard to the device C, it is known that consuming devices such as luminous discharge tubes or bulbs require a higher voltage to start'the discharge than to maintain it when once started. Hence the power factor of this type of load is always below unity. Hence it is necessary to have some reactive device in order to stop the current rising after the discharge has been started. It has been found that by the provision of the non-inductive load C connectedacross the winding A additional'loading at unity power factor has been added to thecoutput of the transformers, thus giving a higher total power factor which has been found to be desirable.

ing devices subject to a larger variation of re- The invention has the advantages of providing for the desired adjustability without loss of secondary voltage due to poor coupling of primary and secondary windings as in the step-up leakage type,and having improved power factor due to the reactive effect of the auxiliary winding acting directly on both primary and secondary windings instead of on one winding only.

I claim:

A step-up transformer comprising a closed magnetic circuit, close coupled primary and secondary windings on one limb of said closed magnetic circuit a branch magnetic circuit, an auxiliary winding disposed thereon, said branch being separated from the said closed magnetic circuit by an air gap, the said auxiliary winding being connected in series with the primary winding, and wound in a direction to produce in the limb on which the close-coupled primary and secondary are wound a magneto-motive force in a direction contra to the normal, whereby the secondary output can be adjusted, and a degree of automatic adjustment or output to load obtained.

CHARLES WILLIAM GALTON. 

